Imports of package controller

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
github.com/moby/buildkit/client
github.com/moby/buildkit/solver/pb
github.com/moby/buildkit/util/progress
github.com/opencontainers/go-digestPackage digest provides a generalized type to opaquely represent message digests and their operations within the registry.
sync/atomicPackage atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms.
timePackage time provides functionality for measuring and displaying time.